Is it just me or does the God Mode have a bit of fiddliness to it, I mean it works but not always and not all the time, most battles it seems to not affect the losses caused by enemy charge, and sometimes large units seem to still take damage. Maybe I'm doing something wrong with it, but other times it works perfect, on the other hand unlimited mana works fine, but the spell cooldowns don't seem to work for me :/ again there is more issue with the fiddliness than anything else/ Great trainer otherwise!
I've personally not had this problem. But the way I've had this option consistently work for ms is to, while in mid-battle or in deployment phase, I enable the option and click on all the units I want to not take casualties, one by one. You can leave the option on for the duration of the battle with no side effects.
I've only ever lost 3-8 units, and that was just because I may have missed clicking on a unit.
But the unlimited mana option has always been a bit fiddly in my experience as far as I know. I rarely use it as I personally find I don't need it with a fully maxed out lord or wizard. So it's not a concern for me personally.